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S/V LYNX: Why go Hybrid?
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Why do we plan to convert to a Combo Electric/Diesel boat?


This is the question that will spark the biggest debate about our choices in setting up S/V Lynx.  We know, because the debate about hybrids vs diesels is heated on the various boat forums out there, with the majority of the debaters calling for diesel boats, not electric hybrids.  But what if you could have both in a combo system?  Read on.

Going Green

People have asked us if we plan to go with a diesel/electric hybrid system because we want a ‘green’ boat?  The answer is, ‘no’.  It’s not that we don’t want to save our planet, we just have other more selfish reasons for our choice in propulsion.  We want the comforts that we get from an electric propulsion system, but also want the security of the power of the diesels. 

On the electric side, we get many advantages, such as less noise and diesel fumes when running off of the electric propulsion system.  The boat will carry more battery power which is also useful for air conditioning at night (without a generator running).  There will be fewer trips to a fuel dock and far less times carting jerry cans of fuel in a dinghy.  We will also have an endless supply of electricity to replace fuel and propane while we are in remote areas. 

However, even though ‘going green’ is not our main reason for adding electric propulsion to our boat, if in the pursuit of our comforts, we also help put less CO2 into the air, we’ll take it.  How much?  Well, that’s open to debate.

Making solar panels and Lithium batteries require energy and that generally adds CO2 into the atmosphere.  How much?  Well, there have been studies done on this.  I found one such study on the making of solar panels that tells us it will take the first two years of service just to make back the energy that was used to make the panel.  However, if the panel lasts for 10 years (or more) then those other eight years are making carbon-free energy, helping reduce CO2 output.  So, they will make us, somewhat, green.

But what about those Lithium batteries?  Again, a study was done on a 30 kWh car battery that showed it would take three and a half years of a gas-guzzling vehicle, or more than 50,000 kilometers before the lithium car would start beating the gas car on carbon-dioxide emissions.  Still, eventually, it does save CO2.

This means adding an electric pod motor system will make us a bit more green than not doing so.  We’ll take it.  But remember, we are not doing this to go green, yet we take it if it helps.  According to these two studies, it will.

One final note on a 'Green' boat.  Some folks want to go completely 'green' by not having a diesel generator or (in our case) that and diesel motors.  In other words, they don't want to burn a drop of diesel, ever.  We would love to do that!  However, our calculations show it just isn't feasible or safe, at this time.  To make it feasible we would need far more energy dense batteries, something along the lines of ten times, or more and you would need more solar (which is unlikely since we are already using all the available space). 

65% use of a 38.4 kWh bank is about 25 kWh of the usable power without stressing the cells.  That amount of power will motor us for about 3 hours at 5 knots.  5 kWh of solar gives us 25 kWh back a day, which takes us about 3 more hours motoring.  That's fine for a trip that only requires that much motoring.  However, on a long passage, you run into a problem.  Your 5 kWh solar array can only recharge 25 kWh a day.  Even if your batteries can hold 250 kWh, it would take ten days of sitting to recharge them and they would currently weigh 10,000 lbs!

So, unless solar panels magically become far more productive (they won't, gains are in small percentages) and batteries become ten times more dense, you still have a problem.  Now, if batteries became 60 times more dense, your range would be around 900 miles... that would be close to the range of most diesel boats.  However, don't hold your breath on getting 60 times more dense batteries any time soon! 

Alternatively, if batteries became 20 times more dense, and you increased your bank to three times larger, you could about match a diesel boat's range, then recharge at port (or by sitting on anchor for a month!).  This is slightly more feasible.  You would eliminate the weight of the diesel motors and replace it with the weight of the additional batteries.  However, without significantly increasing the output of solar panels (which isn't happening), getting a battery that is 20 times more energy dense than current lithium batteries is pretty useless.  Thus, you still need a diesel generator for range and diesel engines for enough thrust (for emergencies) to make a hybrid a safe blue water boat.

Conclusion, we aren't getting rid of diesel fuel anytime soon.

Now, as to the question of safety.  The issue is, a reasonably powerful electric propulsion system that would equal 110 hp (twin 55 hp diesel motors, in our case) would require far too large a battery bank to power very large electric motors.  15 kw motors, like the Oceanvolt system, are really only going to add about 30 hp of power.  You would need to go with four of these to have enough power.  Therefore, you would need 77 kWh of battery storage.  That 77 kw battery bank (which would have to be full at the moment of the emergency) would only power you for one hour at full thrust in all four motors.  For longer than that, you would need two 30 kw diesel generators!  Those are pretty large and expensive.  All total, you are looking at a system that would cost something like $160,000 and weigh quite a bit, there would be over 1,200 lbs in just the batteries!  It's much cheaper and more efficient (in terms of burning diesel in an emergency situation) to just have the 55 hp diesel motors.  However, if we just have those, then we lose all the benefits of an electric propulsion boat, and there are many advantages!

So, the best way for us to get all the comforts and fuel savings an electric boat offers, yet still have the power and range of diesel engines for emergencies, we plan to go with  a combo system of the twin 55 hp diesel engines plus two 7.5 kw electric pods with around 38,400 kWh of batteries.

The negatives for going Hybrid over sticking with just Diesel
1) The first negative: the High Cost to convert a diesel boat to a Hybrid

Well, that's an issue because it is really expensive.  Four Oceanvolt ServoProps cost an insane $100,000.  You need $2,000 worth of solar panels, about $13,000 worth of Lithium batteries (77 kw), $20,000 for a 20 kw generator, and there are a few other costs as well.  Call it $130,000, minimum and with all the small extra things you need, it would top $140,000 installed.

This is a reason why we recently came up with Plan A, which was going with just two SD15 motors for $36,000.  That would also reduce battery size by half to 38,400 kWh ($6,500).  This would reduce the total cost a bit to $70,000.  The problem is that we would be underpowered during an emergency, though fine for normal uses.

However, now we have come up with Plan B, which saves us nearly $46,000, making the price to add the pod system $30,000.  Read on.

OK, still too expensive?   Not so fast.  Perhaps it is better to say, a large initial outlay of money.  As we have shown above, you will save fuel over time.  How much?  That entirely depends on your passages, how many, how far, and the cost of fuel.  On our 142,000 nautical mile,
meandering, double circumnavigations of the world, done over fifteen years, calculating every projected passage (which we have done, see 'Route'), we calculate that (at current average diesel prices, and assuming they don't go up), we save about $50,000 in fuel costs (it varies depending on where you buy fuel, this is a current average).  We also save in other types of maintenance as well, due to using the generators or engines less hours.  In addition, we save in propane, since we will convert everything to electric devices.  For Plan A, that's about $37,000 over the sixteen years.  For Plan B, we save about $15,000 (more on why this is less, later).  In total, for upgrading to the hybrid system, between fuel and maintenance savings we save $87,000 with Plan A for a net gain of $17,000.  That's not bad.  Or, even better, we achieve a net savings of $47,000 if we go with Plan B!  Now we are talking!  Note, this is assuming the price of diesel does not go up... if it does, then we save even more money on either plan.  This is very likely over the 16 years, fuel prices are bound to go up. 

Also, don't forget that new technology always starts out expensive and then, typically, it goes down every couple of years and gets better at the same time.  The cost to convert to a hybrid should drop over time.  If the past is any indication of technology and price, not too far into the future, the cost will be the same as diesels, and eventually become even cheaper.   In two more years, when we buy our system, prices might be even better.  Regardless, even at today's prices, we think going Hybrid with Plan A or B is worth the initial outlay of cost if you factor in the rising cost of diesel.  However, at $30,000 outlay, Plan B is a much lower risk in case we are wrong about the amount of savings.

2) The Second negative: the Plan A Hybrid would have Less power
We are calculating everything for Plan A off of two 15 kw electric motors.  The manufacturer claims these are near 40 hp diesels (but captains who installed them report they are closer to 30 hp).  If you need more power you must go with larger electric motors or move up to four of these.  We don't want to do either of those choices due to the correspondingly larger battery bank, not to mention the high initial cost.  Nor would we have enough solar panels to charge them back up in a day or two.

An example of this is that one of the boats we are interested in comes with 40 hp diesels, but had the option to upgrade to 55 hp diesels.  Most people opted to upgrade because they felt that 40 hp was underpowered for that yacht.  Therefore, if went with two 15 kw Oceanvolt motors, using 48 vdc, equivalent to 30 hp, our total hp would be 60 instead of 110, making the boat severely underpowered.  Most of the time, this isn't going to matter much since you rarely motor at full throttle.  However, when you are caught in a bad situation more power is sometimes needed.  Fighting a strong current come to mind, as does fighting off a lee shore during a heavy blow.  However, remember this, the same boat that has a 55 hp would do better if they had 75 hp motors.  You can always play the more horsepower is better game.

Still, a minimum horsepower for a given boat to achieve enough thrust to travel at a sustained 9 knots is desirable and two 15 kw electric motors will not supply that kind of power. 

However, for comparison sake, in the route examples below we will explore both Plan A and B against a pure diesel engine boat.
 

The Two Hybrid Options (Plan A and B):

Plan A: Two Oceanvolt SD 15 kw motors and a 20 kw generator:

In this case, the boat's propulsion system would consist of two SD15 motors using a Gori three blade folding propellers and a 38,400 kWh battery bank backed up by two generators, one 20 kw and one 10 kw. 

We don't need the servo prop models for our boat.  The fact is, we aren't buying a performance catamaran.  If we were, things would be different.  We might have less room for solar panels and the boat would average higher speeds.  Therefore, regeneration would be much more efficient and desirable.  But for our boat, that won't be true as our average speed will be more like 7 knots instead of 10.

Example, an SD15 ServoProp generates 1 kw at about 8 knots, but 2 kw at 10 knots.  With our boat, we won't be going much more than 8 knots all that often, and 6 or 7 knots a lot of the time.  Therefore, regeneration isn't that advantageous.  Add in the fact that regeneration slows the boat down by at least half a knot per motor, so you would only want to use it when the boat is sailing at fast speeds.  On a production boat, like we plan to use, you will find that you won't want to use regeneration all that often.  And, on the days where the wind is blowing strongly enough for good regeneration, we won't need the energy to motor anyway, since there is plenty of wind to sail.

So, based on this, it works out better to buy two SD15 motors (the non-servo prop model) using Gori folding props.  This would cut down on the electric motor's computer aided complexity and cost less if we happened to hit something with a brass prop vs. computer controlled blades.  Not to mention, the SD15s are cheaper than the ServoProps by $7,000 per motor.

Plan B: Stick with the existing diesels and add two 7.5 kw pod motors:
So, more data came through from two of the boats using Oceanvolt motors, and they listed a couple of issues.  One boat was struck by lightning and lost all propulsive power since they were a purely electric propulsion boat.  The other boat quit their circumnavigation because they were not generating enough power through regeneration.

Let's start with that second boat.  They only had 2 kw of solar panels and no generator.  Those were both mistakes, in our opinion.  Based on the numbers we ran, you need about 5 kw of solar and a good size diesel generator to extend your range plus a smaller backup generator for safety.  However, this boat also reported only getting about 30 hp equivalence with their SD15 motors.  That is a bit underpowered for our 46' catamaran, which really would work best with two 55 hp motors.  Based on their regeneration numbers and reports on low amounts of horsepower, we had to think twice about that being our main propulsion system.

Now let's talk about the first boat that was hit by lightning.  They had originally gone with the four SD15 motor configuration to get enough horsepower for their large cat.  They did report that his was overkill for most situations, as two would get them by for normal motoring.   However, after being struck by lightning, they decided to get rid of two of their four SD15 motors and install two diesel engines.  Now they can motor off of their two SD15s when they want to, but have the diesel engines as backup for longer range when extended motoring is needed.  Also, in an emergency, they will have more power.  Finally, the diesel engines act as a backup to the electric motors if their boat is struck by lightning again.

So, based on the information gained from these two boats, we got out our pen and paper again and ran some numbers.  We found two 7.5 kw, 48v, electric pod motors that run at higher RPMs (2,500).  If we ditch the SD15 motors and, instead, add these two smaller electric motors, yet keep the existing diesel engines while added two high power alternators (one for each diesel engine) we could have the benefits of both systems. 

This configuration will allow us to get almost all the benefits of the electric drive system.  We could still motor at 5 knots on electric for about 3 hours sending 3.75 kw to each pod motor from the initial charge on the batteries. Plus, we would get another 3 hours of motoring from solar recharge during a sunny day.  That is a total of 6 hours per single sunny trip, which would generally be plenty of motoring time, since we are a sailboat. 

However, those two 7.5 kw pod motors are nowhere near strong enough to deal with an emergency, like a stiff current or lee shore in a strong wind.  However, we would still have the full power of the 55 hp diesels to add to the pod motors when needed.  If we get hit by lightning, we still have the diesels.  As for other times, like entering and leaving port, we have the electric motors, which are better for maneuvering and don't need to be warmed up in the morning.  They are also useful for some regen, when the wind is blowing strongly, or for motor sailing, or drogue effects, etc.  And, we still have big enough battery bank for air conditioning all night, if needed.  Finally, there are significant fuel savings in this configuration (see example passages, below).

And another big bonus, the cost to add this system goes way down compared to Plan A.  We no longer need the 20 kw generator, so that's $20,000 less right off the bat.  We don't have the cost of pulling the old diesels (several thousand dollars).  We don't need Oceanvolt SD15 motors, which cost $18,000 each.  We would need to replace them with the two pods motors, but they only run about $9,000 each plus another $1,000 each for hydraulics to lift them out of the water when not in use.  That is a net savings of $16,000 just on the motors.  Doing the math, that is a total savings of about $36,000 and we have a redundant propulsion system with 110 hp available from the diesel engines in emergencies and two electric pod motors for when slow propulsion is advantageous. 

However, there is no free lunch, so if we go with this, we must deal with the weight penalty of 850 lbs.  (100 lbs each for the pod motors, arms, and hydraulic systems, and then we must add an additional 650 lbs of batteries.  That
is not an insignificant number on a catamaran and cats are seriously affected by weight.   Fortunately, we plan to go with a production cat, not a performance cat.  Therefore, our load carrying capacity soars up from something like 2,500 lbs to 9,000-13,000 lbs (depending on the boat we pick).

However, weight still matters.  That means we will try to reduce weight in other places.  For example, on the Salina 48, we will lop off that stupid rear sun platform, which weighs in at about 400 lbs... and go with normal davits.  That's a good start.  We can change the stainless steel standing rigging to synthetic, that saves about 80 lbs.  And, we'll look for more ways to reduce weight, exploring all the viable options to make this Plan B work.  For example, if nothing else, we can reduce the amount of diesel we keep on board, since we also have some electric propulsion.  Diesel weighs a lot!  A gallon of diesel weighs about 7 pounds, so if we reduce our diesel storage from 127 gallons to 84 gallons, we save that 300 lbs.  However, at the beginning of a long passage, if we want to start off with full tanks, so be it.  With a minimum LLC of 9000 lbs, we can afford that temporary weight.  We will burn away some of that weight as we use up diesel on the passage. 


Below is a comparison of passages on Diesel Boat vs a Hybrid diesel/electric (Plan A and Plan B).


I'm going to hit the highlights, as we see it, and show you why we are considering making the change to add electric motors.  The comparison comes down to these two main factors.

1) On the diesel side: Firstly, diesel engines are far cheaper than setting up a hybrid and come with the boat!  Secondly, diesel engines turning a prop are anywhere from 10% to 20% more efficient than a generator supplying electric power to a motor turning a prop.  Why the percentage range?  It depends on the number of conversions of energy.  If you go directly from a diesel generator, without going to the batteries first, you cut down on some of the conversions.  Hence, there is not as much of a penalty.  At the root, the extra cost of the system, the percentage loss of power, and the overall extra horsepower are the main factors which most proponents of diesel power will use to argue against a Hybrid system.  And, they are correct about these factors!  However, as you will see, this isn't the whole story, there are many advantages for an electric propulsion system as well.

2) On the hybrid or combination side:  The electric system obtains energy from several sources, diesel fuel (generator or engines), solar power, wind generators, and some from sailing regeneration (more on what this is later and why is isn't a significant amount). 

Let's talk about solar first since it is the big one.  A catamaran comes with a large surface area over the salon and cockpit.  If you also add on a stern arch (which we plan to do, see photoshopped image at the bottom of the page), specifically designed to hold more solar panels, it is possible to add around 5 kWh of solar panels to a boat like the Salina 48 or Leopard 48.  Without enough solar, an electric/diesel boat is not as viable for saving fuel. 

Now, some people tell you that your panels will receive about 4 hours of their full rated maximum over a typical day, but we have obtained real world numbers from several cruising boats who tracked their charge rates over time.  For example, one boat has 930 watts of solar and gets about 5 kWh a day from that into the batteries (while in the tropics).  That means, on a typical sunny day, on a boat with 5 kWh panels, we will supply about 24 to 25 kWh of energy back into our batteries.  This does not take you quite as far as you might imagine, in fact, 25 kWh will only last for about 3 hours of motoring at 5 knots (more on that below).

Here are the passage examples that I will use:

1)      Short passages of less than 6 hours.
2)      Single day passages during daylight, going 60 miles.
3)      Single day passages during night, going 60 miles.
4)      Single day passages during daylight, going 90 miles.
5)      Two day passages with two days of sunlight, going 260 miles.
6)      21 day passages across an ocean, with steady trade winds, going 3,024 miles.
7)
   21 day passages across an ocean, with steady trade winds, crossing the equator, going 3,024 miles.
8)      21 day passages across an ocean, becalmed in the middle for a week, going 3,024 miles.

For comparison sake in these examples, here are the boats we are using (this data comes from captains on real boats):

1) For the diesel boat we are using a 46' catamaran, fitted with 54 hp diesels. With one engine running they reported burning only a half-gallon an hour at 5 knots.  That's good fuel economy!  Some cats report more like 3/4 of a galleon an hour.  However, we'll go with this more efficient number to give the diesel boat its best numbers.

2) For the Plan A hybrid, we are also using a 46' catamaran equipped with the  Oceanvolt SD15 motors and Gori 3 blade folding props.   At 5 knots they used 3.75 kw of power, each.  Unlike the diesel, you need to run both SD15 motors, so the total consumption was 7.5 kw.

3) For the Plan B hybrid, we will still use a 46' catamaran equipped with two 7.5 kw electric pod motors and two 55 hp diesel engines.  The pods will still use 3.75 kw of power, each, or 7.5 kw total to push the boat at 5 knots.

Note: I'm getting numbers on the OV motors from two real world sources.  One captain's boat has one SD15 ServoProp and one SD15 with a Gori propeller.  He reports that the SD15 with the Gori prop uses, and I quote, 'half the electricity at the same revolutions then the ServoProp'.  The other captain is running two SD15 ServoProps and reports that running at 7 knots he uses 7.5 kw per SD15 ServoProps, 15 kw for both.  Now, for our fuel comparisons I am reducing the speed of our catamaran to 5 knots, this will drop our ServoProp consumption numbers down to 3.75 kw for each motor, or 7.5 total.  However, we know from the other captain that you only use half that power with the SD15s using a Gori prop.  So, the total required output would be 3.75 kw.  However, just for arguments sake, let's assume it is the same efficiency as the ServoProp.  That means 15 kw (total) gets you 7 knots.  Reducing to half speed (3.5 knots) would reduce your power requirement by 8, so about 2 kw.  But, if we only reduce from 7 knots to  5 knots, that should require about
7.5 kw (total).

To get that number, I am using the standard calculation of the required propulsive power increasing to the cube of the speed.  This means that to double your speed requires eight times as much power.  Or reducing your speed by half only requires 1/8 the power.  So, reducing from 7 knots to 5 knots, all total, the motors use 7.5 kw to move at 5 knots.  This means, for a battery bank of 38.4 kWh, with a usable 25 kw, you can motor for just about 3 hours (22.5 kWh) leaving 2.5 kWh for house needs.

That jives with the stats from another catamaran using a new Volvo electric sail drive motor.  They state that it travels 27 NM @ 5 knots on a 40 kWh battery.  They are probably only using 80% DOD.  That would make their consumption about 7.4 kw.  So, that is about the same, around 7.5 kw (3.75 per motor) to motor at 5 knots which confirms our numbers.

For the primary generator on Plan A, we're using a 20 kw DC generator, which burns 1.6 gallons of fuel when outputting its maximum 20 kw of power.  However, figure a 20% conversion loss on generated power.  The example cat will be equipped with a
38.4 kWh battery bank, allowing for 25 kWh usable Lithium batter discharge (about 65% if we keep the charge level between 20% and 85% to make the batteries last longer).

For the Plan B Hybrid, we add high output 48v alternators that put out 100A, or about 4.5 kw per hour, per motor running (again, losing 5% when sending that power to the batteries).  We'll figure .75 gallons an hour for a 55 hp diesel engine.

I am also using the 50% motoring rule, which means you sail 50% on a typical trip and motor the other 50%.  This data is gathered from many different captains. 

Note, I am not figuring in any regeneration from sailing with the props turning backwards in these examples since this is only viable on very windy days or it slows the boat down too much and, therefore, doesn't really save much fuel.
 

Example One:

Short Passage of Six Hours or less (36 nautical miles or less trips)

This is a 6 hour trip, leaving at 8 am arriving at 2 pm.

Diesel Cat:
Burning at .50 gallon an hour, and motoring for 50% of the trip, means 3 hours of diesel motoring, so 1.5 gallons burned.

Plan A: OV Hybrid Cat:
Motoring on battery power for the first 3 hours and sailing the other 3 hours means zero diesel used.

Plan B: Combo Pod motor and diesel Hybrid Cat:
Motoring on battery power for the first 3 hours and sailing the other 3 hours.  This means zero diesel was used.

Winner: Plan A or Plan B Hybrid by 1.5 gallons per passage.

 

Example Two:

Single Day Passage During Daylight (60 nautical mile trip)

This is a 10 hour trip, leaving at 7 am arriving at 5 pm, averaging 6 knots.

Diesel Cat:

Burning at .50 gallon an hour, and motoring for 50% of the trip means 5 hours motoring, so 2.5 gallons was burned.

Plan A: OV Hybrid Cat:
Motoring on battery power for the first 3 hours and sailing for 5 hours followed by 2 hours of motoring off of solar recharged batteries.  This means zero diesel was used.

Plan B: Combo Pod motor and diesel Hybrid Cat:
Motoring on battery power for the first 3 hours and sailing for 5 hours followed by 2 hours of motoring off of solar recharged batteries.  This means zero diesel was used.

Winner: Plan A or Plan B Hybrid by 1.5 gallons per passage.

 

Example Three:

Single Day Passage During Night (60 nautical mile trip)

This is a 10 hour trip, leaving at 10 pm arriving at 8 am, averaging 6 knots.

Diesel Cat:
Burning at .50 gallon an hour, and motoring for 50% of the trip means 5 hours motoring, so 2.5 gallons burned.

Plan A: OV Hybrid Cat:
Motoring on battery power for the first 3 hours and sailing for 5 hours followed 30 minutes the 20 kw diesel generator running.  Calculating a 20% conversation loss, they send 7.5 kw to the motors while sending about 10 kWh to the batteries.  They can then motor on battery power for the final hour.  We used 0.8 gallons of diesel, though they arrive with very low batteries.

Plan B: Combo Pod motor and diesel Hybrid Cat:
Motoring on battery power for the first 3 hours and sailing for 5 hours followed 2 hours motoring on a single diesel engine.  This sends just 9,000 watts back to the batteries (200 amps) for house uses and maneuvering when we arrive.  We used 1 gallon of diesel.

Winner: Plan A Hybrid by 0.2 gallons per passage better than the Plan B Combo boat and 1.7 gallons better than the diesel engine only boat.

 

 

Example Four:

Single Day Passage During Daylight (90 nautical mile trip)

This is a 15 hour trip, leaving early at 4 am (dark) and arriving at 7 pm (sunset).

Diesel Cat:

Burning at .50 gallon an hour, and motoring for 50% of the trip means 7.5 hours motoring, so 3.75 gallons was burned.

Plan A: OV Hybrid Cat:
Motoring for the first 3 hours on batteries.  Then sail during the day for 7.5 hours, recharging the batteries via solar.  Then they motor on electric for another 3 hours.  At the end of the trip, they fire up the generator for an hour while recharging the batteries about 10 kWh.  The motor on battery power for the last half hour.  They used 1.6 gallons of diesel.

Plan B: Combo Pod motor and diesel Hybrid Cat:
Motoring for the first 3 hours on batteries.  Then sail during the day for 7.5 hours, recharging the batteries via solar.  Then they motor on electric for another 3 hours.  At the end of the trip, they fire up the diesels for 1.5 hours of motoring while recharging the batteries some for House needs.  They used 1.13 gallons of diesel.

Winner: Plan B Combo boat by 0.47 gallons per passage better than the Plan A hybrid boat, and 2.62 gallons better than the diesel engine only boat.

 

Example Five:

Two Day Passage with Two Days of Sunlight (260 nautical mile trip)

This is a 43.5 hour trip, leaving at 11 am, arriving on the second day at 5:30 am.

Diesel Cat:

Burning at .50 gallon an hour, and motoring for 50% of the trip means 21.75 hours motoring, so 10.89 gallons was burned.

Plan A: OV Hybrid Cat:
They motor the first 3 hours on batteries, then regain 25 kWh, via solar recharge, each of the two days.  That is a total of 50 kWh which is about 6 hours of motoring time.  All total, they will motor off batteries for 9 hours on this voyage.  That still leaves about 12.75 hours out of  the total 21.75 that they need to motor.  They run a diesel generator for 2.5 hours, sending 25 kw to the batteries then motor for 3 hours off the battery charge.  That leave them with 7.25 hours motoring still required.  They run the generator for 2.5 hours and motor off batteries again for 3 hours.  Now they are 1 and 3/4 hours motoring from their destination.  They run the generator for one hour and motor off batteries for the final 3/4 hours.   All total, the generator ran for 6 hours, so they burned 9.6 gallons of diesel.


Plan B: Combo Pod motor and diesel Hybrid Cat:
They motor the first 3 hours on batteries, then regain 25 kWh, via solar recharge, each of the two days.  That is a total of 50 kWh which is about 6 hours of motoring time.  All total, they will motor off batteries for 9 hours.  That still leaves about 12.75 hours out of  the total 21.75 that they need to motor.  They run a diesel engine for 6 hours, sending 27 kw to the batteries from the alternator.  They switch back to the pods and go for 3 hours on batteries. They are still 3.75 hours short, so they motor for 3 hours, sending 13.5 kw to the batteries, then motor for one hour (leaving some for House uses).  All total, they ran one diesel engine for a total of 9 hours, so they burned 6.75 gallons of diesel.

Winner: Plan B Combo boat by 2.85 gallons per trip over the Plan A Hybrid and 4.14 gallons over the Diesel boat.

Example Six:

21 Day Passage crossing the Atlantic, with Steady Trade Winds (3,000 mile trip).

Being typical a Trade Winds crossing, we can figure that we will only have to motor for two 3 hour stints, like early morning or during the night. 

Diesel Cat:

Burning at .50 gallon an hour, for 6 hours a day for 21 days equals 63 gallons of diesel.

Plan A: OV Hybrid Cat:  
They motor the first 3 hours on batteries.  Then they charge up 25 kWh via solar power, each day, allowing them to motor for another 3 hours each day. This covers the motoring needed for the first day but they need an extra 3 hours each day thereafter.  They run their diesel generator for 2 hours each subsequent day, putting 15 kWh into the batteries.  They use 7.5 kWh to motor the final hour needed and the other 7.5 kWh for House needs.  They ran their diesel generator for 2 hours for 20 days, or 40 hours total.  At 1.60 gallons an hour that equals a total of 64 gallons burned.
 
Plan B: Combo Pod motor and diesel Hybrid Cat:
They motor the first 3 hours on batteries.  Then they charge up 25 kWh via solar power, each day, allowing them to motor for another 3 hours each day. This covers the motoring needed for the first day but they need an extra 3 hours each day thereafter.  They run one diesel engine for 2.5 hours each subsequent day, putting 11.25 kWh into the batteries.  They use 3.75 kw for the final half hour of motoring off electric, leaving the rest for house needs.  They use their diesel engine for a total 50 hours.  At .75 gallons an hour that equals a total of 37.5 gallons burned.

Winner: Plan B Combo boat by 26.5 gallons per trip over the Plan A Hybrid and 25.5 gallons less than the Diesel only boat.

 

Example Seven:

21 Day Passage crossing the Equator, with Steady Trade Winds (3,024 mile trip).

This is a bit of a different trip.  With the Trade Winds, you only need some minor motoring. For sake of argument, we will still figure in motoring for the occasional 3 hour stints, like early morning.  That, and this time, we will calculate in the crossing of the equator as 3 days of no wind.

Diesel Cat:

Burning at .50 gallon an hour, for 6 hours a day out of 18 equals 54 gallons of diesel.  Plus, three days of motoring 24 hours a day is 36 gallons additional for a total burn of 90 gallons.

Plan A: OV Hybrid Cat: 
They motor the first 3 hours on batteries.  Then they charge up 25 kWh via solar power, each day, allowing them to motor for another 3 hours each day. This covers the motoring needed for the first day but they need an extra 3 hours each day thereafter.  They run their diesel generator for 2 hours each subsequent day, putting 15 kWh into the batteries.  They use 7.5 kWh to motor the final hour needed and the other 7.5 kWh for House needs.  All total, they ran their generator during those 17 days for 34 hours. 

However, on three days they were becalmed  in
the doldrums.  During those three days they must motor 24 hours a day instead of six.  They still regain 3 hours of motoring from solar each day, leaving 21 hours of remaining motoring still needed each day.  While running the generator, 7.5 kw goes to the motors to keep moving while 10 kWh gets stored in the battery bank per hour.  Recharging the batteries takes 2.5 hours.  So, each 2.50 hours they regain a full charge allowing 3 hours of motoring.  To motor that extra 21 hours requires about four such cycles, per day, which alsoleaves them enough extra power for house uses.  So each day they motor for 10 hours with the generator running burning 16 gallons of fuel, or a total of 48 gallons.  They add that to the other 17 days where they only had to run the generator for 2 hours a day, which equals 34 hours and they get a total run time of 64 hours, or 102.4 gallons of fuel burned.


Plan B: Combo Pod motor and diesel Hybrid Cat:
They motor the first 3 hours on batteries.  Then they charge up 25 kWh via solar power, each day, allowing them to motor for another 3 hours each day. This covers the motoring needed for the first day but they need an extra 3 hours each day thereafter.  They run one diesel engine for 2.5 hours each subsequent day, putting 11.25 kWh into the batteries.  They use 3.75 kw for the final half hour of motoring off electric, leaving the rest for house needs.  They use their diesel engine for a total 42.5 hours.  At .75 gallons an hour that equals a total of 31.88 gallons burned during those 17 days.

However, on three days they were becalmed  in the doldrums.  During those three days they must motor 24 hours a day instead of six.  They still regain 3 hours of electric motoring from solar each day, leaving 21 hours of remaining motoring still needed each day.  While running one diesel engine, 4.2 kWh gets stored in the battery bank per hour.  Every two hours they gain 1 hour of electric motoring (with some left for house needs).  So, they run on the diesel engine for 14 hours and electric motor for 7 hours.  All total, they run the diesel engine for 42 hours during those three becalmed days.  At .75 gallons an hour, they burn 31.5 gallons.  Add that to the 31.88 gallons from the other 17 days and you get a total diesel usage of63.38 gallons.

Winner: Plan B Hybrid by 39 gallons per trip over the Plan A Hybrid and 26.62 gallons over the Diesel boat.

 

Example Eight:

21 Day Passage crossing the Equator, becalmed for seven days (3,024 mile trip).

Diesel Cat:
Burning at .50 gallon an hour, for 6 hours a day out of 14 equals 42 gallons of diesel.  Plus, seven days of motoring 24 hours a day when becalmed is 84 gallons for a total burn of 126 gallons.

Plan A: OV Hybrid Cat: 
Everything is the same as the voyage above, but now they use their generator, burning 3.2 gallons a day for 13 days and 16 gallons a day for 7 becalmed days.   That totals 153.6 gallons burned.

Plan B: Combo Pod motor and diesel Hybrid Cat:
Everything is the same as the voyage above, but now they run one diesel for 13 days for 2.5 gallons (32.5 gallons).  Plus, for seven days, they have to run one diesel for 14 hours a day, using 73.5 gallons during the 7 days becalmed.  That plus the other 32.5 from the 13 days is 106 gallons total.

Winner: Plan B Hybrid by 47.6 gallons per trip over both the Plan A Hybrid and 20 gallons less than the Diesel only boat.


Important note on reducing speed:
With either electric motoring option, you can alway sacrifice speed for distance.  Though you can reduce speed on a diesel engine, it is most efficient to run them at certain minimum RPM, so going very slow is not as efficient.  This is not true of electric motors, which run fine at any speed, even the slowest.  The rule about power is such, and I quote, "For a displacement boat making way through the water, the required propulsive power increases in proportion to the cube of the speed."  This means that if you want to double your speed, you need eight times as much power or, conversely, to go half the speed your boat requires eight times less power.


If you reduce your electric motors speed to half, for example, going from 7.5 knots to 3.75 knots, your batteries which motored  you for 2.5 hours will now motor for 20 hours.  So, technically, if you slow down enough, like to 3 knots, you don't have to burn any diesel on a long becalmed voyage if you don't want to, all you have to do is sacrifice time for distance and let the solar panels recharge the batteries.

Example Passages, Our Conclusion:

In the examples we listed, the Diesel boat always burns more diesel fuel than the Plan B boat and in all but two cases when compared to Hybrid Plan A (the two exceptions are the becalmed for 3 or 7 day ocean crossings).  However, when comparing just the two Hybrid plans, the Plan A only ties in short voyages and loses to the Plan B in mid range or longer passages.  Therefore, when it comes to fuel savings, the Plan B boat wins, hands down.  If you figure in the additional $46,000 initial cash outlay, the Plan A boat is far more expensive!  Hence, we plan to go with Plan B.

 


Diesel Boat has Greater Range Myth:

One thing we keep reading from forums or hearing on Youtube videos is that diesels have greater range than a hybrid electric or combo electric/diesel boat due to the diesel fuel being more energy dense and conversion losses in an electric hybrid system.  This is just not true, assuming you use a large enough solar array.  Let's use the same 48' cat with 55 hp diesels against our Hybrid or Combo options.

1)      Diesel Boat: Let’s say your boat has a 100 gallons fuel tank and uses 0.75 gallons an hour at 5 knots.  That means the diesel boat can motor for 133 hours, or 666 nautical miles.

2)      Hybrid Boat, Plan A: The first day we get a free 3 hours of motoring (about 15 miles) plus 15 from solar recharge. Each additional day we get 3 hours of motoring from solar recharge of the batteries, for another 15 miles.  The two electric motors use a total of 7.5 kw to push the boat at 5 knots.  You have to run the generator for 2.5 hours to recharge the battery bank (7.5 kw goes to the motors and 10 kWh gets stored in the batteries).  This will recoup the 25 kWh you used from the batteries.  During that recharge time you travel 12.5 nautical miles.  Then, you get to motor for 3 hours off of the recharged batteries, going and additional 15 nautical miles without the generator running.  So, about every 5.5 hours, you travel about 27.5 miles and burn about 4 gallons of diesel.  Converting this to a day, you use about 17.44 gallons a day to travel 120 miles.  With 100 gallons you go about 5.75 days before running out diesel.  Of course, you also get to add the extra 12.5 miles from solar each day, going an additional 72 miles during that period.  Finally, add the initial 30 miles you went on batteries the first day.  All total, you travel about 792 miles, about 126 miles more than the pure diesel boat on the same amount of diesel fuel.

3) Combo Boat, Plan B: With our diesel engine/electric pod hybrid, things are even more interesting.  Each day we get 3 hours of pod motoring from solar recharge.  Then, we use a single diesel engine for about 6 six hours and recharge the battery bank (and add some energy for House needs) and then motor for 3 hours on batteries.  So, each day we use the diesel engines about 16 hours, burning 12 gallons of fuel.  If we divide that into the 100 gallons the example boat carries, we get just over 8 days.  At 5 knots, you travel 120 nautical miles a day, so we go 960 miles before we run out of fuel.  As you can see, our range from a Plan B boat is far more!  This is due to recharging batteries from solar and while motoring we use the more efficient diesel engine (compared to loses with a generator system).  This is not a surprise, we get the best fuel mileage advantages of a diesel boat and the best advantages of an electric boat.  (NOTE: this does not factor in added weight of 850 lbs for the electric system, so that may lower this fuel savings a bit).

However, we're not a motor boat, we're a Hybrid sailing boat!

In either Plan A or B, if we only have to motor for 3 hours a day while sailing the rest, our range is unlimited since we get that from solar recharge.  The diesel boat will, eventually, run out of fuel.  This is not perpetual motion, we are gaining  fuel from the sun.  

What about extended stays in areas with no fuel stations?

This is even more advantageous to the hybrid or combo boat.  On these electric boats, time equals fuel.  Every time you sit in some atoll, enjoying your long stay, your batteries are being filled by solar power, in essence, refueling your boat.  Diesels get no additional fuel in these remote locations.  On a Hybrid, your range and, therefore, time in these remote areas is extended to as long as you have food to eat.  You can even keep moving from island to island.  Your range is vastly extended by free solar 'fuel' for propulsion or House needs.

So, as you can see, the ‘diesel has greater range’ is a myth. All it takes for a Plan A or B boats to exceed the range of a diesel boat is sufficient solar panels on board.  In our case, we plan the same 5 kWh total from our panels as in these examples.  As for the Plan  B hybrid, it just has greater range than either other option since it has the advantages of both the diesel boat and a hybrid boat!


Regeneration
What we are talking about here is letting the props turn backwards as the water moves past, generating power back into the batteries.   In essence, turning wind power (on the sails) into electricity stored in the batteries.  Using the Oceanvolt ServoProp system, you could expect to get about 1 kWh per motor while sailing at about 8 knots.  This is slightly above the average sailing speed for our type of comfortable catamaran (see chart below for how much regeneration at what speed).  However, each motor will slow the boat by a half knot, so that's a full knot if both props are used to regenerate!  There is no free lunch.

A full knot means that over a long passage of something like 21 days, if you regenerate, for say, 12 hours a day, it means you lose a knot per hour over 12 hours, or nearly 14 miles of travel a day.  When you multiply that times 21 days, that's  294 miles.  That equals another two full days of travel added to your passage!  If you figure you must motor for half of those two extra days, you burn fuel.  It also takes you an extra two days on the ocean to reach your destination.

servoprop OV_Servoprop
But, not so fast.  There are some ways to make regeneration more efficient.  One is to only regenerate while your boat has enough wind to take it over efficient hull speed (the speed in which your boat now requires more energy to gain the same increase in speed).  Example: If your boat sails at 5 knots in 10 knots of wind, and 8 knots in 16 knots of wind, but suddenly requires 24 knots of wind to go 10 knots of speed (no longer achieving half of wind speed), your efficient hull speed is something just over 8 knots.

This means that, once you have enough wind to push your boat over 8 knots of hull speed, and you choose to regenerate, there is likely enough wind to keep you sailing at that same 8 knots (hull speed).  Basically, you are wasting some of that wind energy trying to push your boat beyond your efficient hull speed.  So, instead, you could spend that wind power on regeneration.  However, this means you will only be regenerating while the wind is blowing something like 20 knots or more (in this boat's hull speed example).  That doesn't happen all that much on a typical trade wind passage, especially with a slower production catamaran.  However, if you only regenerate during these periods of strong wind, you won't likely add much more time to your trip, yet you will regenerate (and, possibly, at even more than the 1 kw/motor gain).

However, remember, if the wind is blowing strongly enough to use regeneration, it is also blowing strongly enough to sail and not be motoring.  Therefore, you aren't using energy sent to the motors and don't need that regeneration power since the solar panels will do the job to keep up the house uses and recharge the batteries to full anyway.  You might as well just sail slightly faster.

Due to this, we don't really plan to use regeneration very often.  If we are sailing in strong winds and the batteries are low, we might do it then, but when the batteries are charged up, why bother?

Slowing Down

There are times when you want to reach a destination at a specific hour, like morning, as the sun is rising.  Getting there too soon means entering in the dark.  If the wind comes up too much, on a diesel boat, you would have to reduce sail to slow down.  However, in the case of an electric boat (Plan A or B), we can use one or both electric motors in regeneration mode to slow us down slightly while leaving the sails up.  If that's still not enough speed reduction, we reduce some sail, yet keep regenerating.  The added benefit here is that we get a little power regeneration while we slow down to arrive at the right time.  This also works well with a standard SD15 (you don't need the ServoProp motors for this benefit).


Drogue effect:
Another advantage to regeneration, especially when sailing on a catamaran, is the drogue effect.  In bigger seas, as you surf down the face of a swell, catamarans can pick up too much speed and then their bows pierce into the face of the next swell.  Often, catamarans will deploy a drogue to slow them down.  If you put both of your electric motors into regeneration mode, with just the right amount of forward throttle, they will slow you down a knot as the boat surfs down the wave, however, as the boat starts to climb the next face, the motors will power you up.  This effect evens out the speed of the boat, somewhat, and gives you some charging of the batteries as well (though, typically, you will burn more than you gain, but it will extend your motor sailing range).  If you are still surfing too swiftly down a wave, add a drogue.  We went one of the adjustable types so we can tailor the drogue effect work with the electric motor drag.
Motor Sailing
While sailing we also have the option of motor sailing.  This is quite a bit different than a diesel boat motor sailing.  Typically, on a diesel boat, once the wind drops to the point where you are only going 3 or 4 knots, most sailors take down their sails and just motor at 5-6 knots.  The reason is simple, the wind isn't going to help them anymore if the diesels are pushing you at 5 knots and there is no point to running a diesel at a low RPM.  That is bad for the diesel and isn't going to save you much fuel anyway.  You might as well put them at their optimum fuel efficient RPM and do that 5-6 knots.

Motor sailing with an electric motor is different.  Electric motors have full torque at any RPM.  Therefore, you can just give them a little power and add, say, 1 or 2 knots to your boat speed, while continuing to sail.  At that low of a power draw, our battery bank can go for something like 24 hours.  Now you can keep the sails up, adding a knot or two to the  motoring speed, getting you to 3 or 4 knots of total speed, without burning diesel fuel.
Wind Generators
These are small turbines on a pole, driven by props turned by the wind.  At maximum rated power, they seem like a pretty good choice for making power, but not so fast.  First off, you can't trust the manufacturer's numbers.  They use a constant stream of wind in a wind tunnel, you probably won't see those same numbers in the real world where the wind is more fickle.  Secondly, those maximum power numbers are for high winds.  For example, in the chart (below) you can see that at 20kt of wind the various manufacturer's models listed output between 140-280 watts per hour.

However, if you are a cruiser circumnavigating the world (like us), and typically going down wind with the trade winds, then seeking sheltered anchorages out of the wind, you aren't going to see a lot of days with that kind of sustained wind. On average, you're more likely going to be down in the 1 to 12 knot category.  Even at 12 knots, the output is only 20-55 watts and below 4 - 6.8 knots of wind you aren't getting any.  So, you are only going to see a small amount of energy gain most of the time.  A single 330 watt soler panel is going to gain a kilowatt in the five hours it is in sunlight, just about matching what a wind generator will output in 24 hours in 12 knots of sustained wind.

If you don't have room for more solar, a wind generator could make some sense.

But, don't forget, wind generators do make noise as they turn, there is a slight danger of spinning blades, and they require eventual maintenance since they have moving parts.  There is also a significant cost to buy one. 

After considering all this, we haven't yet decided if we want one or even two wind generators on board.  If you think about all the days of less than 12 knots of wind, overall, we will gain more power from a additional solar panel than from a wind generator, with no noise.  Sure, there will be days when the sun is blocked yet there is significant wind, and we won't get that solar power, but the number of those days are infrequent, so in those cases we could just run the 20 kw generator for a short period.  Example: if the wind is blowing at 20 knots, a typical amount of gain from the wind generator is 200 kw, or 4.8 kWh in a 24 hour period.  We can run the generator for fifteen minutes and get the same thing.  That is only fifteen minutes of generator noise, then quiet, or 24 hours of hearing those turbine blades.  Yes, that costs us about a half gallon of fuel, but we won't have to do that very often and at a savings of a half galleon of fuel only per time, it would take something like 700 days of doing this to repay the price of buying the wind generator!

We'll look into this further before making a final decision on one or more wind generators, but as of now, we're leaning toward skipping these on S/V Lynx.





WindGenerator
Turbine Silent-X Air Breeze D400 Superwind Silentwind Rutland 1200 Rutland 914i Nature Power

Max power (W @ 12V)

450

250

600

350

420

483

450

400

Wind @ max (kt)

25

22

37

24

28

29

39

24


20kt output (W)

200

230

192

180

140

255

135

280


12kt output (W)

40

50

48

20

45

60

40

55


Cut-in speed (kt)

6

6

5

6.8

4.2

4

5.8

6.1



Combo Electric vs Diesel vs Hybrid Conclusion:
To quote a boat owner who has sailed their cat around the world for five years, he stated, "The single most important thing on our boat is power.  You cannot have enough."

Or, another boat owner who said, "We have a very large battery bank, large enough to run the air conditioning for half the night."  Their battery bank is less than 10 kw.  With 25 kWh of usable power from the 39,400 bank we can run our air conditioners all night, silently, and recharge the batteries in the morning.

All total, over all passages we make on our epic voyage, we could save over 11,000 gallons of fuel (this is a rough estimate, using the two leopard boat numbers, though our boat will be slightly different.  That’s the estimate on how many gallons we save using a combo boat over a diesel engine only cat on our particular voyage.

You also get rid of all the costs, dangers, and hassles of propane, since you are an electric boat, you use all electric appliances, no propane.  So, no time carting them ashore, finding a compatible fill nozzle, going back to pick them up later (in many cases) and paying for propane.
Those are a lot of hassles you either avoid or reduce.
 

However, currently, the cost to upgrade to a Plan A hybrid boat is too steep!  It will take more nearly 10 to 16 years to recoup the initial expenditure (depending on if and how much diesel goes up).  Fortunately, the Plan B option is much less initial expenditure ($46,000 less).  Therefore, we could recoup that expenditure in more like 4-6 years.

Why is it worth even the $30,000 initial outlays of cash?

Comfort!

Here are the comforts we get by having the electric system on board (batteries, solar, etc.):

1) We will be able to run our air-conditioning, all night, while we are anchored in a hot and humid place, without turning on the generator. 

2) The extra stored energy means we can make more water and, therefore, take more showers.  

3) During our double circumnavigation, we save endless time and energy in not having to, find, cart, pour, and filter over 1000 jerry cans of diesel fuel into our tanks.

4) We save 23,000 hours of not smelling exhaust.

5) We save the same 23,00 less hours of  having to listen to a diesel engine. 

6) We are more self-sufficient, able to remain away from civilization for longer, without needing diesel. 

7) We’ll spend less time going to fuel docks.

8) We spend no time searching to find or fill propane bottles.

9)We spend less time doing maintenance on diesel engines and sail drives (mostly due to running the generator or diesels a lot less hours, so maintenance cycles are further apart).  

10) We can motor sail (silently).

11) We can use regeneration for a drogue effect to even out the motion of the boat.

12)We have instant power at any time without warming up the diesels.  This is good in port, and may help to complete a tack.  Even if the pods are raised, it takes less than 20 seconds to put them in the water with the hydraulic system we will use.

13) We save time and fuel not having to warm up two diesel engines every time we leave port.

14) We have more power for charging all our toys.

So, how do you put a price on comfort?  If we have to cough up $30,000 extra to refit the boat for Plan B... so be it!  Most, if not all, of that initial coast will be regained in the first 5 years and we will save money in the long run.  However, we expect prices to come down in the next three years, so maybe this initial cost will become a bit less. 

Comparing the two Hybrid Plans, Plan B is far less for initial cash outlay and saves more money in the long run, but adds weight to the boat.  Then there is the safety issue.  When it comes to safety concerns, the Plan B boat wins, hands down.  After all, it has two separate propulsion systems which can combine to have more power than the diesels and far more than the Hybrid Plan A.  It is also safer if we are hit by lightning.  On the down side, the Plan B boat has more maintenance costs (one additional diesel, since it has two engines and a generator vs two generators).  It also has two sail drives that need serving.

Still, the Plan B Combo boat seems to be the better option, cheaper and safer, yet retains most of the advantages of a Hybrid system boat.

So, currently; based on the comforts gained, safety, and cost, Plan B is the route we will choose to go during our refit of S/V Lynx.  However, here are the two system setups (Plan A and Plan B):


The Plan A Hybrid Setup for S/V Lynx (this is now our 2nd choice; see Plan B below for our 1st)
1) Two Oceanvolt SD15 electric sail drive motors with Gori props:

Oceanvolt SD15
Synchronous permanent magnet electric motor.
Sail Drive with 1.93:1 reduction.
Lightweight: weighs as little as 42.5kg (motor & sail drive).
The only complete electric inboard propulsion system with
EMC certified closed circulation liquid cooling providing both cooling and lubrication.
Functions as a hydro generator to generate power while under sail.

Gori three blade folding prop:
We wold go with a couple these with a Gori folding prop, to quote their site,
 
"The 3-blade Gori folding propeller marks a technological and functional leap forward in the development of propellers for sailboats. It is now possible for sailboats and motorsailers to gain the folding propeller's speed advantages under sail, combined with the fixed propeller's thrust capability when motoring. The 3-blade Gori folding propeller was introduced on the market in 1994 and won the DAME award and HISWA award the same year, as the best new marine product.

"OVERDRIVE" FUNCTION
The 3-blade Gori folding propeller's "overdrive" function adds a new dimension to sailing under power. The helmsman can choose the propeller pitch and profile in the water while sailing forward, by regulating the yacht's shift and throttle control. Without the use of vulnerable hydraulics or complicated mechanical devices.

The "overdrive" is used when motorsailing in fair weather or when using the engine under sail. The "overdrive" gives the same speed at lower rpms. The result is less engine noise, less vibration and better fuel economy."




GoriSD15
2) 38,400 kWh lithium battery bank:

This number isn't random.  The typical amount of energy we could recoup in a day of good sunlight is 25 kWh which is also the usable power from this size bank, if we keep the batteries between 20% and 85% charge.

With a single sunny day at anchor, we can net 25 kWh of solar, which refills our bank completely.  Assuming we are using power for a lot of house needs, certainly in 2 days we can recoup a full battery charge for the next voyage using just solar regeneration. 

batteries
3) Five kilowatts of solar panels:

Solar panels are critical to the Hybrid system being viable.  You must regain a lot of power from the sun or you are just burning diesel up through a less efficient generator.  To that end, if we go with a Salina 48 or Leopard 46, we plan to build a special stern arch.  This will extend the coach roof line.  We are also adding a hard top over the helm, which will add a little more space for solar panels.  These are being added to increase our total solar panel array.  On the Salina 48, we can get to over 5 kw.

On the right are two photoshopped images of a Salina 48, showing the arch we plan to add to the stern.  This arch will not increase the length of the boat, since it ends at the same distance out as the sugar scoops.  To keep the weight down, we plan to build this out of carbon fiber.
   We will also squeeze in panels on the regular coach roof and Helm roof.
SternArchSternSolar
4) One 20 kw and One 10 kw (or slightly smaller) Diesel Generators:

The 20 kw (closer pic to the right) is the main workhorse, which can push the boat to 7.5 knots, running both SD15 motors if needed or supply power to the battery bank as well as the motors when running at 6 knots or less.  This generator weighs 320 lbs.

As a backup, there will be a lighter 10 kw generator (farther pic to the right), capable of sending 5 kw to each motor to push the boat at 4 knots or, while at anchor, we can run this generator to recharge the batteries or run the A/C saving some fuel since we don't need the power of the big 20 kw generator.  This generator weighs a maximum of 260 pounds if we go with the 10 kw generator.  (We hope the boat we buy comes with the smaller generator already).

In an extreme emergency, after battery power is exhausted, we can run both electric motors at maximum thrust by running both generators at the same time, giving us 30 kw, supplying 15 kw to each of the two SD 15 motors.
  They can then run, flat out, for as long as the diesel fuel holds up.
20kw10kwGen
5) Diesel Fuel tanks

We plan to keep the existing diesel fuel tanks, (127 gallons on the Salina 48, 185 gallons on the Leopard 48, and 248 gallons on the Saona 47).  Most of the time these will be kept fairly empty, holding perhaps 50 gallons of diesel for emergencies since most of the time we will run without any diesel usage at all.  However, when facing a long passage, or a long time away from civilization, we can top off the tanks.  Sailing with just 50 gallons of diesel saves a lot of weight!  On the Salina 48 it saves us 539 lbs, on the Leopard 48 is saves 945 lbs, and on the Saona 47 it saves us 1386 lbs.!  The two generators plus the batteries and SD 15 weigh a total of 1095 lbs.  Or, if you look at the Salina 48, after removing the diesel engines and sail drives, and reducing to 50 gallons of diesel, even with the entire hybrid system on board the boat weighs 339 pounds less, the Leopard 48 weighs 745 lbs less and the Saona weighs 1186 lbs less!


The Plan B Hybrid Setup for S/V Lynx (and our current top choice)
PROPULSION:

Two Aziprop 7.5 kw Fischer Panda Pod motors

2500 rpm
28 Nm
48 volt
18.7 kg (41pounds)

These electric pod motors will be used for the majority of our propulsion needs.  Here are examples:

1) When entering or exiting port, or moving around an anchorage.  They don't have to be warmed up, are virtually silent, and have excellent low speed properties since electric motors have full torque at zero RPM.

2) During a passage when we want to motor sail.  They put out no fumes are virtually silent, and at low power usage can go for a very long time on batteries.

3) For limited motoring when the wind drops (up to about 3 hours).

4) For regeneration, drogue, and just slowing us down (on purpose), on some occasions.

To cut drag, these pod motors will be mounted on arms that are raised with a hydraulic motor.  Here is a link to a video showing a system that does this (these are no longer sold though, but we will make a similar system).

https://www.youtube.com/watch?v=nl1a_ACQmvs

Two Yanmar or Volvo 55 hp diesel engines
These engines will come with the boat.  These will rarely be used compared to the electric pod motors.  We plan to use the diesel engines for three purposes:

1) On a long passage where we must motor for more than three hours, continuously, as the diesels are more efficient in fuel use than a generator supplying power to an electric motor.

2) To heat water and charge batteries using a High Output alternator
while motoring.
(100 ah at 48 volt, one on each engine)

3) In emergencies, when high power and thrust are needed, like when fighting a current or in a large blow with a lee shore.

FlexoFold three blade folding prop:
When it comes to the diesels, based on reviews and tests, we plan to use Flexofold 3-Blade sail drive Folding propellers.  The strengths of these props are as follows:

1) Low drag: Compared to fixed props, these folding props increase the sailing speed of the boat by 1 to 2 knots (since there are two of these in the water all the time).
2) Maximum Speed: They are the highest rated for speed of all the folding and feathering props we have seen in tests, up to a knot faster than the competition.  (See test result below)
3) Pulling power in forward (bollard test):  Again, they achieved top marks in this test, which means when we are fighting a headwind, going against a current, etc, these pull the boat forward better than other options. (See test result below)
4) Simple: Compared to feathering props, these are simpler to maintain and have less cost in rebuilds.

To the right are the 2015 Yachting Monthly posted results from their tests on speed and bollard pull ahead:

Note, though stopping power wasn't as good as some of the other props, that is not as much of an issue with our boat since we also have two electric pod motors to aid in bringing the boat to a stop when needed.

On folding props:
Though we were interested in the Gori props, research shows that using them on a sail drive is hard on the transmission if you try to use their 'overdrive' feature, which requires you to go from reverse to forward without stopping in neutral first.  With the electric drives this was less of a concern.

Also, though there have been reports of both Gori and Flexofold props coming off in rare cases, the Flexofolds have more mechanisms for keeping the prop on the shaft where the Gori props only have two, tightening the bolt and using loctite.  The Flexofolds have these two methods plus a metal tab washer with a nut and bolt system that bends the metal washer to keep either the bolt or the separate nut from backing out.

Pod
DieselFlexofoldMax Speed
Bollard
2) 38.4 kWh lithium battery bank: (800ah at 48volts)

This number isn't random.  The typical amount of energy we could recoup from solar in a day of good sunlight is 25 kWh, so recharging a 38.4 kWh 70% is very doable since you won't ever completely deplete it.

In just one sunny days at anchor, netting 25 kWh of solar, we can recharge and are good to go.  However, with House needs, we will often spend two days at anchor before any long passage or use the generator for a short time to top off the batteries.  But, when we have time, in 2 days we can recoup a full battery charge for the next voyage using just solar regeneration. 

We have not settled on exactly which batteries we will buy yet, but are leaning toward LifePO4, DIY option (see Solar and Batteries).  But, we are hoping for better choices in the next couple of years as battery technology changes and prices continue go down (hopefully).

Battery
3) Five kilowatts of solar panels:

Solar panels are critical to the Hybrid system being viable.  You must regain a lot of power from the sun or you are just burning diesel up through a less efficient generator.  To that end, if we go with a Salina 48 or Leopard 46, we plan to build a special stern arch.  This will extend the coach roof line.  We are also adding a hard top over the helm, which will add a little more space for solar panels.  These are being added to increase our total solar panel array.  On the Salina 48, we can get slightly more than 5 kw.

On the right are two photoshopped images of a Salina 48, showing the arch we plan to add to the stern.  This arch will not increase the length of the boat, since it ends at the same distance out as the sugar scoops. 
We will also squeeze in panels on the regular coach roof and Helm roof (see image, right).

NOTE: even though the original sun deck is shown in these images, if we go with a Salina 48 we plan to remove that deck completely and add a different dinghy lift system.
SternArchSternSolar
4) One 10 kw (or slightly smaller) Diesel Generator:

Our 9 - 10 kw generator is for use while we are at anchor if we run out of battery power.  The generator  can run the A/C or recharge our batteries of the solar isn't keeping up.  We hope to buy a boat that comes with this smaller generator already, but will add one if needed.

10kwGen
5) Diesel Fuel tanks

Because we are keeping the diesel engines and a generator, we will need the existing diesel fuel tanks, (127 gallons on the Salina 48, 185 gallons on the Leopard 48, and 188 gallons on the Leopard 46).  Some of the time these will be kept less than half full, holding perhaps 50 gallons of diesel for emergencies since most of the time we will run without any diesel usage at all for short trips and very little for midrange passages.  However, when facing a long passage, or a long time away from civilization, we will top off the tanks. 

Sailing with just 50 gallons of diesel saves a lot of weight!  On the Salina 48 it saves us 539 lbs, on the Leopard 48 is saves 945 lbs, and on the Leopard 46 it saves us 966 lbs.!  This offsets the weight of the added electric propulsion system, yet still gives us plenty of range (about 360 miles motoring between the diesel engines and electric pods, more if we are willing to slow down).  On short passage days, this is more than sufficient since we will likely be sailing most of it anyway.
90% of our planned passages are less than that distance so why not save the weight?